#include <iostream>
#include <string>

using namespace std;

int len[128];

int main() {
  while (true) {
    int n, k;
    cin >> n >> k;
    if (n == -1) break;
    
    string a, b;
    cin >> a >> b;
    len[0] = a.length();
    len[1] = b.length();
    
    for (int i = 2; i < n; i++) len[i] = len[i-1] + len[i-2];
    while (n > 1) {
      if (k <= len[n-2]) n -= 2;
      else {k -= len[n-2]; n--;}
    }
    if (n == 0) cout << a[k-1] << endl;
    else cout << b[k-1] << endl;
  }
  
  return 0;
}